Musnad Ahmad 27:1577

'Ali ibn 'Ayyash narrated to us, Al-Layth ibn Sa'd narrated to us, Nafi' narrated to me, that 'Abdullah ibn 'Umar informed him that a woman was found killed in one of the military expeditions of the Prophet, may Allah bless him and grant him peace. The Messenger of Allah, may Allah bless him and grant him peace, disapproved of the killing of women and children.